Diagnosis of post-stroke depression (PSD) is extremely difficult due to concomitant focal cognitive disturbances or generalized intellectual impairment, and, in some cases, dissociation of mood and affective behavior.

The diagnosis has been standardized on the basis of psychiatric criteria in the Diagnostic and Statistical Manual (DSM) - III, an approach that has been criticized for taking into account non-specific stroke-related somatic symptoms.

Yet evaluation of the PSD diagnosis by comparing the severity of depressive symptoms in stroke to an age-matched population sample and by conducting a controlled antidepressant treatment study in unselected PSD patients has failed to disclose any evidence that non-specific symptoms influence the diagnosis of PSD.

The prognosis, however, of early vs late diagnosed PSD and the response to treatment of early vs late diagnosed PSD differ, indicating that PSD diagnosed according to DSM-III criteria covers a heterogeneous group of etiologically different conditions.